Nano-silicon and nano-calcium enriched biochars mitigated salt stress in safflower by enhancing ion homeostasis and root growth

Abstract

Soil salinity hampers crop growth and productivity by impairing root functions due to nutrient deficiency and/or reduced water uptake. The carbon-rich soil amendments may reduce these adverse effects of salinity on plants. Based on this hypothesis, the objective of this study was to evaluate the physiological changes and growth of safflower (Carthamus tinctorius L.) roots under salt stress (non-saline, 6, and 12 dS m⁻¹) in response to various biochar treatments (control, 30 g kg⁻¹ solid biochar, 30 g kg⁻¹ nano-silicon dioxide enriched biochar, 30 g kg⁻¹ nano-calcium carbonate enriched biochar, and a combination of 15 g kg⁻¹ nano-silicon dioxide + 15 g kg⁻¹ nano-calcium carbonate enriched biochars). The biochar-related treatments greatly reduced sodium uptake and enhanced soil pH, cation exchange capacity, and nutrient contents of plant roots. Root length, weight, and density were noticeably enhanced by solid and especially enriched biochars under both saline and non-saline conditions. The biochar-related treatments decreased root lignification and osmolytes such as proline, glycine betaine, soluble carbohydrates, and proteins by increasing root water content, which helped to improve shoot mass and grain yield under salt stress. The findings of this study demonstrate that pure and particularly nanoparticle-enriched biochars have great potential to enhance root and shoot growth of safflower plants under salinity by improving soil properties and reducing salt toxicity.